Hypochlorite induces lipid peroxidation in blood lipoproteins and phospholipid liposomes

The accumulation of lipid peroxidation products reacting with 2-thiobarbituric acid (TBARS) has been observed both in very low density blood lipoprotein (VLDL) and suspensions of liposomes prepared from VLDL phospholipids incubated with hypochlorite. Butylated hydroxytoluene (BHT) completely inhibited TBARS formation at a concentration of 100 microM, at which it decreased the concentration of hypochlorite in the absence of liposomes only by 7%. The formation of lipid peroxidation products in course of the incubation of egg yolk phospholipid liposomes with hypochlorite has been revealed using three methods: (1) measurement of TBARS, (2) measurement of additional amounts of TBARS resulting from the introduction of excess Fe2+ to peroxidized liposomes (delta TBARS), and (3) measurement of the chemiluminescence flash amplitude appeared upon the addition of Fe2+ to the suspension. The results obtained by all these methods were similar: Lipid peroxidation products were accumulated during the first 2 to 3 h of liposome incubation with 100 microM hypochlorite, and the amount of lipid peroxidation products accumulated after incubation was directly proportional to the initial hypochlorite concentration. These data suggest that hypochlorite can initiate lipid peroxidation both in lipoproteins and phospholipid liposomes.